The broad, long-term objectives of this project are to determine the contributions of ErbBt (EGFR/HER1) and related molecule ErbB2 (HER2/neu) to breast cancer invasiveness, intravasation and metastasis. The contributions of these molecules to tumor cell motility and invasion rather than growth could be significant and not addressed by normal clinical trials. There are three specific aims that will evaluate particular aspects of the contributions of ErbB1 and ErbB2 to invasion and intravasation. The first aim will examine the possible activation of the EGF/CSF1 paracrine loop by other receptor/ligand pairs besides just EGF and CSF1 and the involvement of other stromal cells. The second aim will explore in more detail the elements of the ErbB2 molecule that contribute to invasion and metastasis. The third aim will compare the contributions of specific molecules to in vivo invasion and intravasation. These objective will be achieved using a variety of breast cancer models including breast cancer cell lines, transgenic models of breast cancer, and xenograft models of patient cancer. In vivo invasion measurements will be made using imposed ligand sources. Multiphoton imaging of multiple cell types using fluorescent protein labeling will define the relationships and motion of both tumor and stromal cells in the primary tumor microenvironment. The relevance of this work is in improving our understanding of how breast cancer spreads away from the primary tumor. By identifying the mechanisms by which tumor cells can move out from the primary tumor and enter blood vessels, we hope to identify new ways in which metastasis can be attacked.